Multi-Mode Phase-Shifting Interference Device

Abstract

A multi-mode interference (MMI) device includes a substrate layer, a core layer deposited on the substrate layer for propagating an optical signal, and a cladding layer deposited on the core layer for guiding the optical signal. The core layer includes a core section suitable for propagating multiple optical signals having different wavelengths. The core section includes a shifting segment for uniquely shifting phases of the multiple optical signals. The shifting segment includes at least one or a combination of sections having different effective refractive index, a tilted segment, a curved section, and waveguides with variations in width, thickness or effective refractive index.

We claim: 
     
         1 . A multi-mode interference (MMI) device, comprising:
 a substrate layer;   a core layer deposited on the substrate layer for propagating an optical signal; and   a cladding layer deposited on the core layer for guiding the optical signal, wherein the core layer includes a core section suitable for propagating multiple optical signals having different wavelengths, wherein the core section includes a shifting segment for uniquely shifting phases of the multiple optical signals, wherein the shifting segment includes at least one or a combination of sections having different effective refractive index, a tilted segment, a curved section, and waveguides with variations in width, thickness or effective refractive index.   
     
     
         2 . The MMI device of  claim 1 , wherein the MMI device manipulates the optical signal according to a predetermined task, and wherein a combination of structural phase shifting components of the shifting is optimized for the predetermined task. 
     
     
         3 . The MMI device of  claim 2 , wherein the predetermined task includes splitting the multiple optical signals or combining the multiple optical signals. 
     
     
         4 . The MMI device of  claim 2 , wherein the shifting segment includes a tilted section having a first part and a second part, and wherein at least a portion of the second part of the tilted section is modified with a patch changing an effective refractive index in the core section. 
     
     
         5 . The device of  claim 4 , wherein the multiple optical signal includes a first signal having a first wavelength and a second signal having a second wavelength, wherein the first part of the shifting segment adds a −π/2 phase shift to the first signal, and the second part of the shifting segment adds a −π/2 phase shift to the second signal. 
     
     
         6 . The MMI device of  claim 1 , further comprising:
 an input section for accepting the multiple optical signals including a first signal having a first wavelength and a second signal having a second wavelength; and   an output section having multiple output ports for outputting separately the first signal and the second signal.   
     
     
         7 . The device of  claim 6 , wherein the input section includes a 1×2 MMI coupler, and the output section includes a 2×2 MMI coupler. 
     
     
         8 . The MMI device of  claim 6 , wherein the shifting segment includes a first shifting segment arranged in parallel with the input section and a second shifting segment arranged in parallel with the output section, wherein the second shifting segment is tilted with respect to the first shifting segment, and wherein a portion of the shifting segment includes a patch of material having an effective refractive index different from a material bordering the patch. 
     
     
         9 . The MMI device of  claim 1 , wherein the core layer includes a first uniform section and a second uniform section, wherein each of the first uniform section, the second uniform section and the core section of the MMI device has two lateral edges and two end edges, wherein the sections are connected by corresponding lateral edges, and the end edges of the sections form edges of the MMI device, wherein the core section include a patch having a material with an effective refractive index different from a material of an area bordering the patch, wherein the patch has lateral and end edges, and wherein the lateral edges of the patch are tapered. 
     
     
         10 . The MMI device of  claim 1 , wherein the core section includes multiple waveguides having variations of at least one of a width, a thickness of an effective refractive index of a material of a waveguide. 
     
     
         11 . A method for manipulating an optical signal according to a predetermined task by a multi-mode interference (MMI) device, comprising:
 determining a combination of structural phase shifting components manipulating differently multiple optical signals having different wavelength according to the predetermined task; and   fabricating the MMI device having a substrate, a cladding layer and a core layer including a core section suitable, at any point, for propagating the multiple optical signals, wherein the core section includes the combination of structural phase shifting components.   
     
     
         12 . The method of  claim 11 , wherein the structural phase shifting components are selected from a group consisting of sections having different effective refractive index, a tilted segment, a curved section, and width or thickness variations. 
     
     
         13 . The method of  claim 11 , wherein the MMI has multiple core layers and cladding layers, and part of the upper core layer is etched to create difference in effective refractive index. 
     
     
         14 . The method of  claim 11 , wherein the core layer includes an indium gallium arsenide phosphide (InGaAsP) material, and the substrate and the cladding layer includes an indium phosphide (InP) material. 
     
     
         15 . The method of  claim 11 , wherein the core layer and the substrate includes a Si material, and the cladding layer includes silicon dioxide.